If you're serious about wanting viable third-party candidates, then you need to start by changing a system which makes it virtually impossible for third party candidates to be viable.

The quickest path to this would be instant run-off voting. The ability to say "I like this guy best, but if he doesn't win then I'd prefer the guy who isn't completely insane" would instantly free voters who feel trapped (and are trapped) by the current dynamics of the two-party system. (Some people talk about proportional assignments for the house of representatives, but that tends to just strengthen the party machine while silencing independent voices.)